The Irish surname Magill, also rendered McGill, is an anglicized form of the Gaelic name Mac an Ghaill which means, literally, "the son of a foreigner or stranger". It was not the name of a native Irish clan but rather was adopted as a Gaelic patronymic by the Stapletons, a Norman family who came to Ireland in the wake of the Anglo-Norman invasions of 1170, settling in counties Kilkenny and Tipperary and becoming thoroughly hibernicized.

As is usual with "Mac G" names, the composite "Mag" form, in this instance,Magill, is the one generally used in east Ulster where the name is most numerous, while the full prefix is retained in west Ulster. It should be noted that many Ulster Magills/MacGills are descendants of Scottish mercenary forces (the gallowglasses) and MacGills from Scotland were also among the proprietors introduced by the Plantation of Ulster in the early seventeenth century. These MacGills/Magills originate from the Scottish clan Mac a' ghoill, meaning "descendant of the lowlander".

Notable bearers of this name include Patrick MacGill, the county Donegal poet and novelist, and Michael Samuel Magill, an Operations Technical Leader at EDS